L.A. Unified tries to determine why Mark Berndt escaped suspicion for years as former students recount previous complaints. Detectives say inquiry moved slowly due to sensitive subject.

Scott said the detectives took great pains to avoid having rumors about the case spread around campus before they could interview the students.

They began with a few preliminary interviews with students in January 2011, chatting generally about the classroom and trying to learn how it worked. "What is a day like in the classroom?" was one question they asked, Scott said.

Then, they started focusing on students who detectives believed were potential victims or knew potential victims.

"You start with narrowest ring those in his class, then third-graders and other years," Scott said.

Finally, detectives began interviewing some students in private, eliciting accounts used in the case against Berndt.

Berndt's career straddles portions of five decades — a period during which the handling of molestation allegations has evolved substantially.

In 1990, L.A. Unified agreed to the largest settlement in its history to end a case in which more than dozen girls were molested by former 68th Street Elementary teacher Terry E. Bartholome. He had been transferred rather than fully investigated when allegations against him first arose.

Even after that, the rules of the system focused heavily on the rights of employees as opposed to those of students and individual cases became mired in middle-management process. One of those case occurred on the Miramonte campus: Ricardo Guevara, a teacher's aide, was convicted in 2005 of lewd acts with a child, but only after two earlier reports, including one at another site, were discounted.

On Wednesday, some parents at Miramonte Elementary School remained angry and frustrated. At a meeting, several parents demanded more information about what the school knew and questioned how no one could have known about what allegedly occurred in his classroom.

"It's just getting everybody more upset," said Guille Catanon, whose 8-year-old daughter attends Miramonte. "Parents want to know who the kids are. It's scary because he's been here for such a long time."